In the picture we see the power supply space, fitted with the bundled dust filter.
Installing 5.25" drives is a tools free process, made possible with Cooler Masters lock/open system. It doesn't get much easier, and it's a feature that Cooler Master often implements in their cases.
There's space for a total of 6 3.5" hard drives and a 2.5" drive in the CM 690 II Advanced case. The 6 dedicated bays consist of 2 hard drive cages, with the first one containing 4 bays, and the last 2 in the other cage. The bottom cage can be mounted in such a way that a 120x240mm radiator can be installed in the bottom of the case as well. The cage also supports a 120mm fan, if you need more cooling for the hard drives, but the front fan should be enough.